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It Don’t Mean a Thing, That First Day of Spring

Published: March 19th, 2012

COMMENTARY
By Michael D. Lemonick

It’s that wonderful time of year again, and no, I don't mean March Madness. March 20 marks the first day of spring, a fact that newscasters and TV meteorologists and The Weather Channel will be making their usual fuss.

But the truth is, we don’t really care about the first day of spring, which is simply the date when daylight and darkness last equally long. We care about the onset of spring weather and all it brings — flowers blooming, birds chirping, that sort of stuff. And what we’ve designated the first day of spring is only loosely related to all of that. If you live in Maine or North Dakota or northern Minnesota, the flowers and such come long after March 20, and if you’re in southern Mississippi or Alabama, it comes well before.

This strange mistiming is mostly just a glitch of the weather: next winter could easily be unusually cold. Until the full onset of human-caused global warming, however, the ups and downs balanced out, with no long-term trend.

Not anymore, though: over the past several decades, spring weather has been coming steadily earlier on average, and that affects more than when we start going on picnics. All sorts of biological processes are triggered by warmer weather — not just flowering, but animal migration and giving birth and the shedding of winter coats and the emergence from cocoons and much more. This annual timing (which also applies to leaf fall and return migrations and more in the autumn) is broadly known as phenology (not to be confused, Wikipedia warns us, with phrenology).

As the planet has warmed, many of these spring events have been creeping gradually earlier, a direct result of global warming. The changes don’t happen at the same rate for all species, though. Here’s what Jake Weltzin, director of the USA National Phenology Network said in a live online chat on the topic last week:

“…some organisms respond strongly, whereas others don't respond at all, or respond in directions opposite of what one would predict. So, this has great potential to create mismatches in how organisms interact . . . what we call a trophic mismatch. And, we also see that organisms that are active earlier in the year tend to be most responsive to changing environmental drivers (especially temperature).”

In short, what once would have been a smoothly integrated ecosystem can go haywire. In one recent study, for example, scientists pinpointed how bird migration patterns have changed in a warming world, leading some birds to arrive before or after their favorite food sources are at their peak. Another study points out the timing mismatches that affect plants and the insects or other animals they depend on for pollination. The list is pretty much endless when you start to look into it.

Nobody actually knows how well ecosystems will weather these changes, but it’s a safe bet that there will be big disruptions in some places. After all, the plant and animal species in any given ecosystem have learned over thousands of years to live together; they’re like an old married couple, multiplied by many millions.

I wrote a few weeks ago about how nice it is to have had a warm winter, and I’m not sad to see the flowers starting to bloom. But I’d also like the local ecosystem to survive intact over the next several decades, and it occurs to me that if winters become significantly warmer, the summers could, too — a pretty unpleasant prospect.

The first day of spring itself still won’t have a tight connection to spring weather as the planet warms. And while I’m used to saying “oh, right — it’s still likely to be pretty chilly for another month,” at least I’ve got the mismatch pretty well figured out, having lived in the same place for long time. Before long, though, my instincts, along with those of the birds and the bees, will be out of date.